p2p: improve and test eofSignal

p2p/peer.go

@@ -300,7 +300,7 @@ func (p *Peer) dispatch(msg Msg, protoDone chan struct{}) (wait bool, err error)
 		proto.in <- msg
 	} else {
 		wait = true
-		pr := &eofSignal{msg.Payload, protoDone}
+		pr := &eofSignal{msg.Payload, int64(msg.Size), protoDone}
 		msg.Payload = pr
 		proto.in <- msg
 	}
@@ -438,18 +438,25 @@ func (rw *proto) ReadMsg() (Msg, error) {
 	return msg, nil
 }
 
-// eofSignal wraps a reader with eof signaling.
-// the eof channel is closed when the wrapped reader
-// reaches EOF.
+// eofSignal wraps a reader with eof signaling. the eof channel is
+// closed when the wrapped reader returns an error or when count bytes
+// have been read.
+//
 type eofSignal struct {
 	wrapped io.Reader
+	count   int64
 	eof     chan<- struct{}
 }
 
+// note: when using eofSignal to detect whether a message payload
+// has been read, Read might not be called for zero sized messages.
+
 func (r *eofSignal) Read(buf []byte) (int, error) {
 	n, err := r.wrapped.Read(buf)
-	if err != nil {
+	r.count -= int64(n)
+	if (err != nil || r.count <= 0) && r.eof != nil {
 		r.eof <- struct{}{} // tell Peer that msg has been consumed
+		r.eof = nil
 	}
 	return n, err
 }